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African Institute of Tropical Ophthalmology (IOTA), Bamako (J.-F.S., A.G., L.T.), MALI
Mopti Regional Centre for Ophthalmology, Mopti (A.A.B.), MALI
GTZ Primary Health Care Project, Sévaré (V.J.), MALI
Centre René Labusquière, University Victor Segalen Bordeaux 2, Bordeaux, FRANCE (D.M.)
Address reprint requests to: Dr. Jean-François Schémann, 9 rue de Calais, 75009 Paris, FRANCE. E-mail: jfschemann{at}wanadoo.fr
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSCONCLUSIONACKNOWLEDGMENTSREFERENCES |
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Methods: Using a randomized two level cluster sampling, 20 clusters of 75 children aged six months to six years were selected for evaluating xerophthalmia (XN night blindness and/or X1B Bitot spot). Concurrently stature and weight were determined. A semiquantitative seven-day dietary questionnaire was applied to the mothers of 484 infants to assess consumption of vitamin A rich foodstuffs. The prevalence of biochemical deficiency was attested using the Modified Relative Dose Response test (MRDR) on a sub-sample of 192.
Results: Of the studied children, 4.3% (95% Confidence interval [CI]: 3.2–5.3) reported night blindness and 2% (95% CI: 1.3–2.7) had Bitot spots. Prevalence of xerophthalmia attested by at least one of these signs was 5.4% (95% CI: 4.2–6.5). The prevalence reached 10.5% at three years of age. The MRDR test proved abnormal in 77.1% of the subjects (95% CI: 70.3–82.7). Serum retinol was lower than 0.35 µmol/L in 43.8% (95.6% CI: 36.9–51.3) and less than 0.70 µmol/L in 92.7% of the children (95% CI: 87.8–95.8). Weekly consumption of vitamin A rich food was rare: 75.8% had not eaten any animal vitamin A rich food, and 22.1% had consumed less than seven times a vitamin A rich food of either vegetable or animal origin.
Conclusions: These data define vitamin A deficiency as a severe public health problem in the Bandiagara area of Mali.
Key words: xerophthalmia, vitamin A deficiency, Mali, MRDR, nutrition
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSCONCLUSIONACKNOWLEDGMENTSREFERENCES |
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The GTZ Primary Health Care project in Sévaré, which planned to add a vitamin A supplement program during the National Immunization Days (NIDs), solicited the support of the African Institute of Tropical Ophthalmology (IOTA) to evaluate vitamin A deficiency in the Bandiagara district among preschool children.
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METHODS |
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Sampling Methods
The study was conducted from March 26 to April 20, 1997. The sample was recruited using a randomized two-level cluster sampling method, following procedures recommended by the World Health Organization (WHO) blindness prevention program method [6].
The 1987 national census list of villages served as the sampling frame for the area [7]. No urban or rural stratification was retained for the selection procedure. A required sample of 1465 children six months to six years of age was estimated, based on an expected prevalence of 4%, an alpha error of 5% and a desired absolute precision of 1%. Twenty villages (clusters), were randomly selected, each of 75 children to provide a total of 1500 individuals. If a cluster was too small for recruiting 75 children, the most proximate village should have been chosen for completing the cluster. No design effect was considered in determining sample size.
Two sub-samples were drawn randomly: one child out of every three for food intake inquiries and health status assessment (planned n = 500) and from this later group one out of every two individuals for biochemical status assessment (planned n = 250).
Measurements
Ophthalmologic Examination.
A history of night blindness (XN stage) was obtained by questioning children’s mothers. Three questions were sequentially asked to ascertain if the child was able to see during daytime, during the night and, finally, if night blindness was present using a vernacular term (in Dogon "gire nama", in Peul, "pinku" and in Bambara "surofinye"). Children who also had daytime vision problems were excluded.
All children received an ophthalmologic examination by the same ophthalmologist using a X2.5 magnification with a lamp. Clinical signs of xerophthalmia, Bitot spots (X1B) and active or non-active corneal lesions were noted. A categorical variable for xerophthalmia was derived corresponding to the presence of night blindness and/or Bitot spots.
Vitamin A treatment (one capsule of 200 000 IU x 3) was given to children showing clinical signs of vitamin A deficiency and tetracycline ointment was applied in case of ocular infection.
Anthropometry.
Stature (cm) and body weight (kg) were measured by one of the two trained nurses. Infants under two years of age were weighed using a 25 kg Salter hanging scales (CMS Weighing equipment, High Holborn, London, United Kingdom). Children over two years were weighed on scales calibrated before each session. Body weight was measured on children fully dressed (with light clothing) but without shoes.
Infants under two years were measured lying down using a conventional wooden height board. Individuals over two years were measured standing up.
Whenever possible, age was verified on presentation of a birth certificate. Otherwise, it was estimated using a local calendar and history of past events.
These measurements allowed calculation of three standard normal deviate (Z) scores based on reference values from the National Center for Health Statistics (NCHS) published by WHO [8]:
Z-scores under the threshold of -2 were considered as moderate and those less than -3 as severe nutritional deficiency.
Food Survey.
Information about breastfeeding and age for weaning was recorded by questioning the mothers. A seven-day food frequency questionnaire was administered to them to estimate the number of occurrences on which food sources of vitamin A and carotenoid were consumed during the previous week. Trained local health practitioners compiled a list of 21 available foods, six from animal origin rich in retinol and 15 of vegetable origin rich in beta-carotene. Sauces containing vegetables rich in beta-carotene, such as baobab or gombo leaves, which are ingested in very small amounts, were given a weight considered to one fifth of a serving in the intake analysis.
Morbidity.
Two weeks’ history of morbidity symptoms was recorded: episodes of coughing, fever, diarrhea as well as oral intake of rehydration salts. A six-week history of measles and measles immunization and use of vitamin A capsules for the preceding three months were noted.
Biochemical Markers.
Vitamin A status was assessed by measuring serum retinol concentration and the Modified Relative Dose Response test (MRDR), an individual indicator of liver retinal stores [10,11].
Briefly, 200 µg of acetate of 3,4-dehydroretinol (DR) was orally administered. Five hours later, 0.5 mL of capillary blood was extracted by pricking the child’s finger with a vaccination scratch blade and was collected in a "Microtainer Benson Dickson" tube. The tubes were set in a vacuum flask filled with ice and kept dark. Within three hours the tubes were centrifuged at room temperature (1300 x g, 10 min). The serum was fractionated off, aliquots placed on ice for no more than five hours, frozen to -20°C in a deep-freeze at the nearest health center before being taken to Bamako and then shipped on dry ice for laboratory analysis to Grenoble (France). Freezer tubes were thawed slowly to room temperature just before assay. A high performance liquid chromatography assay (HPLC), made up of an isocratic system using silica gel (adsorption) as the stationary phase, was used for dehydroretinol and retinol determination, and 0.5 mL aliquots of serum were extracted. Briefly, proteins were precipitated with absolute ethanol, and the fat-soluble vitamin A was extracted subsequently into an n-hexane phase, and analyzed by automated high-performance liquid chromatography with a Lichrosorb Si 60.5 column. Retinol peak was detected spectrophotometrically at 313 nm. The peaks were integrated by means of Perkin Elmer Chromatography Data Station Sigma 10B system. Cumulative quality-control data for each analysis were provided during the analysis period. Briefly, the coefficients of variation for the estimation of retinol and dehydro-retinol were 3.3% and 3.0%, respectively.
The ratio of DR to retinol was calculated. The performance and reproducibility of this ratio of has been evaluated in different groups with normal and abnormal vitamin A classified status [11,12]. A deficiency is defined as a ratio greater than or equal to 0.06. A prevalence of abnormal tests greater than 20% defines a public health problem. The situation is considered to be severe when the prevalence is over 30% [12]. Serum retinol thresholds used were 0.7 µmol/L and 0.35 µmol/L, reflecting low status and severe deficiency, respectively.
Statistical Analysis
Statistical comparisons were carried out using the chi-square for categorical variables. Continuous data across groups was compared by variance analysis.
Data analysis was carried out using the EPI INFO program, version 6.03.
The protocol was approved by the IOTA’s ethical committee and a consent form written in French language and translated either in Dogon, Peul or Bambara language was signed by the infant mothers prior to the examinations.
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RESULTS |
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Age distribution by age of the survey population was comparable to that observed in Mali as a whole (Table 1). Boys and girls were equally represented (49.6% to 50.4%).
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Wasting was less frequent; 193 children (12.8%) were moderately wasted (W:H < -2 Z score), and 52 (3.4%) severely (W:H < -3 Z score).
Boys tended to be more underweight (p = 0.01) and stunted than girls (p = 0.004). The gender difference was not significant for wasting (Table 2).
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There was no active case of corneal involvement. Only four children had an old corneal opacity that could not be evidently related to a history of xerophthalmia or measles episode.
The prevalence of xerophthalmia varied with age (Fig. 1). No case was found under one year of age. At the age of three, prevalence of night blindness and Bitot spots peaked at 8.5% and 3.3% respectively.
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Biochemical Markers.
From the 250 sample dedicated to biochemical evaluation, 192 have been able to be analyzed: 77.1% (95% CI: 70.3–82.7) of the children were tested abnormal for the MRDR assay; 92.7% (95% CI: 87.8–95.8) had a serum retinol level lower than 0.7 µmol/L and 43.8% (95% CI: 36.9–51.3) lower than 0.35 µmol/L, with the highest prevalence of abnormal MRDR and serum retinol <0.35 µmol/L found among one year old children (Table 3).
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Vitamin A Intake.
Weekly intake of vitamin A rich foods was estimated for 430 children, as 54 children still being exclusively breast-fed, have been subsequently excluded from the analysis (Table 4).
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The average vegetable vitamin A eating occurrences were 20.56.
Twenty-two percent of children had consumed fewer than seven times during this week foods rich in vitamin A, whether animal or vegetable-based.
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DISCUSSION |
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Chronic malnutrition is a consequence of inadequate food and/or illnesses lasting for a relatively long period. About one fifth of the children demonstrated slow growth. In the case of the under-three-years-olds almost one third were affected. These figures are close to the 1996 demographic and health study [13] of under-three-year-olds, which recorded 27.6% of stunted children in the Mopti region. The World Health Organization considers a prevalence of stunting of 30% to represent a vulnerability threshold above which vitamin A deficiency may be suspected to exist in a population, when used as an indirect indicator of risk, in the absence of direct measures of vitamin A status [12]. Wasting indices give an estimate of the body mass in relation to the height as a reflection of the current nutritional status. In this study, 12.8% of the children were affected by emaciation. The figure of 12.8% (17.6% under three years) is slightly better than the one to come out of the 1996 DHS which was 26.6% in the Mopti region, but higher than the WHO threshold of 8% [12]. It indicates a vulnerable population and reflects an troublesome food and nutritional situation.
The prevalence of body weight insufficiency seems low (22.5%) given that stunting was 20.9% and wasting 12.8%. Nevertheless, for children under three years, our results (39.3%) are very similar to those given by the demographic and health study (41.3%).
Vitamin A Status
Xerophthalmia.
The data relating to xerophthalmia must be discussed in relation to the dry season in which the study was carried out. In this season there is a shortage of sources of vitamin A, few fresh vegetable foods are available.
Night blindness is a subjective but valid indicator of vitamin A deficiency [12,16]. The 4.3% rate is therefore higher than the 1% threshold established by the WHO as defining a public health problem in a given community.
Preceding Malian studies had also revealed high prevalence of night blindness: 2% in Koutiala [1], 9% in Douentza [5]. During a national survey in 1996, prevalence ranged from 0.3 to 4.1 depending on the region (2.6% in the Mopti region) [14]. Nevertheless, night blindness diagnosis rests on questions to each child’s mother, and figures should therefore be cautiously interpreted. Nevertheless the disorder is well known, as in all villages a local term existed for the condition.
Night blindness was far more frequent between the ages of two and four years. This period corresponds to the weaning phase when the child switches from mother’s milk to the family cereal-based meal, a group of foods that is poor in vitamin A content and can result in a higher risk of vitamin A deficiency.
The more frequent occurrence of night blindness among boys had been reported in several studies [1–3]. Several explanations may be given: first of all, young girls often stay close to their mothers, joining in cooking-related tasks and receiving more food in the course of a day; also small boys more often suffer from diarrhea, which can involve a loss of vitamin A and an absorption deficit.
Bitot Spots.
Bitot spots are pathognomonic early signs of vitamin A deficiency. The 2% prevalence rate found is higher than the WHO threshold of 0.5%, which designates a public health problem. Bitot spots were also more prevalent in children under three years of age, and also higher in boys than in girls.
These data correspond to those reported in other studies. During the 1996 national Malian survey, levels of Bitot spots ranged from 0.15% to 1.59%, depending on the region (1.09% in the Mopti region). In neighboring countries, the following prevalence were recorded, 4.9% in Benin, 2.69% in Burkina Faso, 1.06% in Chad [15].
Despite a high level of clinical xerophthalmia and a much higher prevalence of biochemical deficiency, no active signs of corneal xerophthalmia were observed. Corneal complications are often the consequence of an attack of severe illness, such as severe measles superimposed on a state of moderate to severe vitamin A deficiency [16]. In our study area, a history of measles was reported in one of ten children during the preceding six weeks, suggesting that the question used may not have been fully understood since no important epidemic had been documented in the region for many years.
MRDR Test.
Vitamin A deficiency attested by an abnormal MRDR test is far more frequent than clinical xerophthalmia [17]. It is important to estimate in a population the number of children suffering from a infraclinical deficiency because they are more likely to suffer from pathogenic events: each year, one million children die worldwide as a result of infections related to vitamin A deficiency and immunocompromised conditions [18].
Serum Retinol.
A serum retinol value only reflects the vitamin A reserves when these have largely been depleted: concentrations under 0.7 µmol/L reflect a low status, whereas a deficiency is said to be severe when the level falls below 0.35 µmol/L. For WHO criteria, a severe public health problem exists when more than 20% of children are situated below the 0.7 µmol/L threshold level or when more than 10% have a level lower than 0.35 µmol/L.
We acknowledge that the MRDR abnormalities (77.1%) are very high as regard to the 20% alarm WHO threshold [12]. Handling procedures have been rigorously conducted and we had continuous evaluation of laboratory processes allowing us to argue for the critical values reported.
These results are quite comparable to those reported in other African areas: 78% of abnormal results in Zambia [19] and 64.8% in Labbé, Guinea [20].
Deficient vitamin A status can usually be found to be associated with chronic, low vitamin A intakes, as we observed in our study population. However, low serum retinal can also be aggravated by an insufficient hepatic protein supply and infection which can affect retinal transport and utilization, respectively [21]. Whichever test is considered, there are far more children suffering from a biochemical deficiency than of xerophthalmia. Indeed when attested by MRDR test, biochemical vitamin A deficiency is 14 times more frequent than xerophthalmia prevalence.
This phenomenon is supported by high xerophthalmia rates, but surprisingly no active corneal disease was observed during the survey. This could be due to the absence of measles epidemic in the population during the past years despite low measles immunization coverage (41.8% in the Mopti region in 1996) [13].
Food Habits
Breast-feeding would be a protective factor in the case of xerophthalmia. Thus in Nepal the risk fell by 61% for children breast-fed [22]. In Bandiagara, almost all of the children aged from 6 to 11 months were breast-fed exclusively, whereas the WHO recommends that from six months upwards, all children should receive supplementary food [17]. The 23.8 months average weaning age is close to the 21.6 months given by the demographic and health study.
In Bandiagara, cereals largely dominate the caloric supply, and children rarely consume vitamin A rich foods. Foods of animal origin are extremely rare, whether this be fresh fish, milk products or eggs for which there is a social proscription (children are not allowed to eat eggs otherwise they will become thieves later in life). Yellow fruits or green-leafed vegetables are not very common; the latter are often consumed in sauces but, given the long preparation times, the carotenoids can be partially destroyed. Some way of preparation of these foods (drying and baking) can significantly lessen the food retinol or beta-carotene content.
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CONCLUSION |
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Prevention measures have been addressed elsewhere [23]. As a follow-up to our study, the Ministry of Health, together with UNICEF decided to distribute vitamin A in the Mopti region during the national immunization days in December 1997. This measure was successful and extended to all regions in 1998.
In addition, it is desirable to improve the production of beta-carotene rich foods by developing gardening and to enhance population awareness on nutrition to promote regular consumption of vitamin A rich foods.
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ACKNOWLEDGMENTS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSCONCLUSIONACKNOWLEDGMENTSREFERENCES |
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Received December 22, 2000. Accepted May 30, 2002.
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REFERENCES |
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